Portions of this invention are very closely related to earlier coowned patent documents directed to optical systems and methods for imaging, and for noticing and optically following a large variety of objects outside an optical system. These techniques included capabilities for “steering” of radiation beams, using any of a great variety of optical-deflection or -switching arrangements.
Such arrangements comprised using pointable mirrors of many different types, and other kinds of routing devices such as an optical-switch “fabric”, and birefringent and other nonlinear materials, all generally positioned within an optical system. The mirrors included individual reflectors, and reflector arrays, over a broad range of sizes and typically controllable in two axes of rotation as well as in some cases piston movement.
Some of the mirrors were microelectromechanical system (“MEMS”) units or other micromechanical devices—i.e. not limited to electrical or electronic control. Among the relatively larger mirrors (for instance those over 5 mm across) were magnetically driven individually gimbaled mirrors using, for example, custom jewel bearings—or etched monosilicon in-plane torsion hinges (or “flexures”).
These earlier patent documents included:    Bowker et al. U.S. Pat. No. 5,467,122, “UNDERWATER IMAGING SYSTEM”;    Lubard et al., U.S. Pat. No. 6,836,285, “LIDAR WITH STREAK-TUBE IMAGING, INCLUDING HAZARD DETECTION IN MARINE APPLICATIONS; RELATED OPTICS”;    Kane et al., U.S. Pat. No. 6,856,718 “HIGH-SPEED, LOW-POWER OPTICAL MODULATION APPARATUS AND METHOD”;    Bowker et al., U.S. Pat. No. 6,873,716, “CONFOCAL-REFLECTION STREAK LIDAR APPARATUS WITH STRIP-SHAPED PHOTOCATHODE, FOR APPLICATIONS AT A WIDE RANGE OF SCALES”;    Gleckler, U.S. Pat. No. 7,227,116, “VERY FAST TIME RESOLVED IMAGING IN MULTIPARAMETER MEASUREMENT SPACE”;    Kane et al., U.S. Pat. No. 7,297,934, “OPTICAL SYSTEM”;    Kane et al., international application PCT/US05/28777, “AFOCAL BEAM STEERING SYSTEM CORRECTED FOR EXCESS DIFFRACTION DUE TO PHASE ERROR FROM MICROELECTROMECHANICAL MIRROR OFFSETS”;    Fetzer et al., international application PCT/US04/00949, “ULTRAVIOLET, INFRARED, AND NEAR-INFRARED LIDAR SYSTEM AND METHOD”;    McLean et al., international application PCT/US06/46535, “MINIATURE INTEGRATED MULTISPECTRAL/MULTIPOLARIZATION DIGITAL CAMERA”;    Kane et al., international application PCT/US07/14992, “CAMERA-STYLE LIDAR SETUP”;    Campion et al., international application PCT/US07/25912, “REFINED OPTICAL SYSTEM”;    Griffis et al., application Ser. No. 10/426,907, “COMPACT ECONOMICAL LIDAR SYSTEM”;    Kane et al., application Ser. No. 11/431,209, “OPTICAL-RADIATION PROJECTION”;    Kane, application Ser. No. 11/796,603 “OPTICAL SYSTEMS AND METHODS USING LARGE MICROELECTROMECHANICAL-SYSTEMS MIRRORS”; and    Hunt et al., provisional application Ser. No. 60/999,159, “OPTICAL SYSTEM WITH MINIATURE SCANNING MIRROR”.
All these documents are wholly incorporated by reference into this present document. The present invention, however, is not limited to teachings in those earlier documents—given that, for instance, mirror adjustments by galvanometer scanner and other steering systems are also applicable.
Among these earlier documents are teachings of a proprietary CatsEye™ object-warning system. These documents teach advanced and excellent apparatus and methods for imaging from aircraft and many other kinds of mounting arrangements, both vehicular and stationary, and in many useful practical applications encompassing, merely by way of example, commercial-airline flight-control imaging e.g. from fixed towers, astronautical rendezvous, ground-planned defense maneuvers, and vehicle collision avoidance, as well as terrain mapping from space.
More specifically the above-mentioned earlier documents teach such innovations with greater field of regard (“FOR”) and field of view (“FOV”) than in prior approaches, and with much more nimble and sophisticated capability to notice and optically follow a large variety of objects outside the optical system, than previously possible. Even the technologies in those coowned documents, however, leave something to be desired in ability to simultaneously acquire images, and parts of images, at different scales or magnifications—with extremely high flexibility and adaptability.
Whereas aperture-sharing and field-sharing innovations in some of those documents do enable simultaneous imaging in different directions and at different magnifications, what remains lacking is ability to change focal properties very quickly, to obtain arbitrary values of magnification. The desirable adjustments mentioned here are not “pixel zoom” features such as found in some digital consumer-electronics cameras. Adjustments of that type commonly produce objectionably coarse images, merely extracted from large fields of pixels.
Rather what is desired is in effect an “optical zoom” chars acteristic, with resulting images limited only by the quality of optical elements. As is well known, however, conventional optical-zoom provisions are strictly constrained to the speed at which macroscopic optomechanical components can be bodily moved. Nevertheless, as will be seen, some such components are compatible with some embodiments of our present invention.
The previously mentioned servoed-mirror components, taught in the coowned patent documents, made major advances in relieving speed and agility limitations of old-fashioned gimbal systems—i.e., for pointing of entire optical systems. What is needed now is relief from the analogous limitations of individual focal elements and focal systems.
It is true that some controllable focal properties are represented in those above-mentioned documents, particularly through the use of servoed-mirror arrays—which can be caused to provide active optical elements that are microminiatures of the famous and enormous astronomical observatories in Hawaii and elsewhere. The servoed-mirror-array approach, however, is relatively expensive—and delicate and fragile as well. Thus there remains a need for individual focal adjustments that are not only easily adjustable and very fast, but also extremely robust and economical.
A particularly troublesome limitation of imaging systems heretofore, especially when such systems are carried in remotely operated observation or mapping vehicles (e.g. aerial drones), is that a remote operator cannot readily see high-resolution images, simultaneously, of both:                a broad region of interest, for purposes of gaining awareness of a situation that is extended throughout the broad region—i.e. so-called “situational awareness”; and        a much narrower area showing important details, in effect a so-called “telephoto view” of features such as vehicles, structures, animals or people.        
Such simultaneous high-resolution images can be obtained if the platform vehicle has plural separate cameras, each having its own objective system with its own separate optical aperture; however, this approach is relatively undesirable. Use of separate systems introduces new problems of image-position alignment (i.e. positional correlation) and parallax, as well as consistent tonal ranges—and of course added operating complexity, weight, cost, and power drain.
People skilled in this field will immediately appreciate that an inability to see such high-resolution images at plural different scales simultaneously (unless two separate objective systems are provided) is extremely disadvantageous. Such inability handicaps the operator severely.
More specifically, the operator either cannot see precisely the details needed to make identifications based on the details, or to take a desired action with respect to the details; or cannot continuously monitor the overall region of interest—to be confident that the situation is not changing importantly while the details are inspected, or while preparations are being made for action. To maximize the probability of success, whether the mission actually is an interdiction or simply a comprehensive inspection, both these kinds of visual information are needed at substantially the same time. An object of our invention is to remove this limitation.
Very-Recent Innovations Known Only in Other Fields:
The following details are not seen either in conventional imaging literature—or in “general” optics papers and patents, if indeed there is modernly such a thing as “general optics”. The formerly unified, or primarily unified, field of optics has now subdivided itself into literally many dozens of individual fields of optics and optronics, all extraordinarily isolated from one another.
These many individual fields actually are documented by corresponding dozens and even hundreds of separate scientific and engineering journals, convocations and seminars—all around the world. It is therefore nowadays in essence a physical impossibility for any one scientist or engineer (or even a sizable laboratory or academic department) to follow all of the literature of “optics”—or of any sizable fraction of the new separate individual fields.
People in these many new subfields do not generally talk to each other, or write to each other, or read each other's literature. Therefore it would not at all be obvious for a typical worker in, e.g., astronautical imaging, to know much if anything about the details taken up below.
Liquid lenses—The discussion here is believed to be, heretofore, unique to the field of cellular telephones. This field is not usually conceptualized as a field of “optics”, but it is common knowledge now that in recent years camera capabilities are provided in some such telephones.
Designers of such equipment have confronted and successfully resolved startlingly difficult problems, to cause those camera functions to be routinely available in cellular phones. Those phones which can take pictures—and receive and send pictures through the cellular-telephone network, as well—are not significantly different from other cellular telephones in weight, reliability, power requirements, or even cost.
One key innovation that has enabled this achievement is the development of a so-called “liquid lens”. The fact that the lens itself is literally liquid enables the lens to be variable in focus. Furthermore the variable focus is controllable electrically. To be specific, a variable electrical charge is applied to deform the meniscus of the lens, and that meniscus is itself a focal surface.
Hence the variable charge thereby changes the effective radius of curvature of the focal surface, and the focal length of the camera. Further specifics of these remarkable devices are set forth in later sections of this document.
Diffractive lenses—The devices under discussion here are most typically controllable Fresnel lenses. These devices too are operated by electrical signals applied to modify focal properties, but the lenses are substantially solid, rather than liquid—notwithstanding their use of so-called “liquid crystals”.
Development in this field is driven not by anything related to cellular telephones, but rather by ophthalmic applications, i.e. so-called “active” eyewear. At the heart of switchable/variable diffractive lenses are nematic liquid crystals, used to implement the desired focal variations.
Historically efforts to develop this technology have met with limited success, for a variety of reasons: in some cases the thickness of the liquid-crystal layers (exceeding 400 μm) made their response low and recovery times long, and their transmission low as well—because of optical scattering. High-efficiency liquid-crystal-based diffractive devices have been demonstrated for beam steering, but less attention has been given to imaging applications.
Recently, however, the University of Arizona has developed a photolithographically patterned thin diffractive lens with large aperture, fast response, and a power-safe configuration for ophthalmic applications. Only a fixed number of Fresnel zones is possible with an active diffractive lens; hence the device has discrete optical powers, leading to a discrete zoom capability.
The University's approach for the active diffractive lens employs a photolithographically patterned thin diffractive lens with large aperture, fast response time, and a power-failure-safe configuration. A diffractive lens, for this purpose, is produced in the normal way used for Fresnel lenses, by “removing” from the refractive lens excess thickness that produces multiple-2π phase retardation—thereby leaving only the optically active focal surface. Such “removing” results in multiple Fresnel zones.
Here, however, each zone is made up of one more corresponding liquid crystals. Each liquid crystal is substantially analogous to the liquid crystals in a common liquid-crystal display (“LCD”), with electrodes used to control optical contrast.
(To be precise, a Fresnel lens is not usually produced by reprocessing an existing refractive lens. Rather, the “removing” is a matter of design, commonly effectuated by casting the Fresnel lens at the outset.)
The phase jump at each zone boundary is 2π for the design wavelength. The outer radius of each zone is analytically derived, and to digitize the process the continuous phase profile in each zone is divided into multiple subzones with a series of discrete phase levels, as will be detailed later in this document. Increasing the number of subzones increases diffraction efficiency, reaching maximum values of 40.5%, 81.1%, and 95.0% for lenses with two, four, and eight phase levels per zone, respectively.
Selection of Fresnel zones electrically—to invoke desired zoom values—is accomplished by applying voltages to electrodes associated with the multiple liquid crystals which make up the lens zones. Such voltage application is closely analogous to the actuation of visible elements in a common LCD.
Alvarez lenses—Additional active-lens technology is also being developed that may be used for the current invention. A worthwhile example is assembly of two so-called “Alvarez lenses” in a Galilean-telescope configuration to build a zoom lens.
As originally conceived some four decades ago, an individual Alvarez lens consists of two complementary phase plates 201, 202 (FIG. 12a), each a transmissive, refractive element with a third-order polynomial surface—and each having a first optical surface that is planar and a second contoured in a two-dimensional cubic profile. When a single such “phase plate” is placed in an optical beam, the plate introduces a phase shift in the beam.
Because manufacture of these refractive plates is very difficult, some workers have concentrated on diffractive versions of Alvarez devices, but for our purposes refractive plates (being faster and having less wavelength dependence) appear preferable. Near the end of this document we present a more-detailed discussion of Alvarez lenses and other alternative zoom-lens systems.
Deformable polymer liquid zoom lenses—Transparent polymer membranes are configured to pump liquid in and out of a lens cavity, by stretching or squeezing a chamber that is filled with the liquid. Contraction caused by squeezing makes the lens more strongly positive; squeezing makes the lens more negative. Furls they details appear later in this document.
Conclusion—As noted above, the present state of the art in imaging, while admirable, leaves considerable refinement to be 2o desired.